VATICAN CITY Pope Benedict XVI basked in an emotional sendoff Wednesday at his final general audience in St. Peter's Square, recalling moments of "joy and light" during his papacy but also times of great difficulty. He also thanked his flock for respecting his decision to retire.

Tens of thousands of people toting banners saying "Grazie!" — "Thank you" — jammed the piazza in Rome to bid Benedict farewell and join the appointment he has kept each week for eight years to teach the world about the Catholic faith.

Benedict clearly enjoyed the crowds, taking a long victory lap around the square in an open-sided car and stopping to kiss and bless half a dozen children handed to him by his secretary.

In keeping with the historic moment, Benedict changed course and didn't produce his typical professorial Wednesday catechism lesson. Rather, he made his final public appearance in St. Peter's a personal one, explaining once again why he was becoming the first pope in 600 years to resign and urging the faithful to pray for his successor.

"To love the church means also to have the courage to take difficult, painful decisions, always keeping the good of the church in mind, not oneself," Benedict said to thundering applause.

He recalled that when he was elected pope on April 19, 2005, he questioned if God truly wanted it. "'It's a great burden that you've placed on my shoulders,"' he recalled telling God.

During eight years, he said "I have had moments of joy and light, but also moments that haven't been easy ... moments of turbulent seas and rough winds."

But he said he never felt alone and thanked his cardinals and colleagues for their guidance and for "understanding and respecting this important decision."

CBS News correspondent Allen Pizzey reported that the Pope said he was "fully aware of the seriousness and novelty" of his decision to resign, and so too seemed the cardinals in attendance -- many of whom will soon be tasked with choosing his successor.

Under a bright sun and blue skies, the square was overflowing with pilgrims and curiosity-seekers. Those who couldn't get in picked spots along the main boulevard leading to the square to watch the event on giant TV screens. Ciro Benedettini, of the Vatican press office, told CBS News that about 150,000 had filled the square.

Many Catholic Americans made the trip to be at St. Peter's on Wednesday, to bid farewell. They were among the masses as Benedict's Popemobile slowly wound through the crowd on its way to the altar.

With chants of "Benedetto!" erupting every so often, the mood was far more buoyant than during the pope's final Sunday blessing. It recalled the jubilant turnouts that often accompanied him at World Youth Days and events involving his predecessor, Pope John Paul II.

Benedict has said he decided to retire after realizing that, at 85, he simply didn't have the "strength of mind or body" to carry on. He will meet Thursday morning with cardinals for a final time, then fly by helicopter to the papal residence at Castel Gandolfo south of Rome. He is expected to give brief remarks upon his arrival to the faithful gathered at the castle to greet him.

There, at 8 p.m., the doors of the palazzo will close and the Swiss Guards in attendance will go off duty, their service protecting the head of the Catholic Church over — for now.

As Pizzey has reported, Benedict has seemed increasingly at ease with his transition into retirement, but he will leave in his wake a Vatican beset by scandal. His successor will have to figure out how to deal with deeply-rooted management problems at the top of the Church, infighting between various factions in its governing body, and the lingering effects of the child sex abuse scandal.

Many of the cardinals who will choose Benedict's successor were in St. Peter's Square for his final audience. Those included retired Los Angeles Cardinal Roger Mahony, the object of a grass-roots campaign in the U.S. to persuade him to recuse himself for having covered up for sexually abusive priests. Mahony has said he will be among the 115 cardinals voting on who the next pope should be.

Faced with questions about overcoming the scandal and improving the church's image, U.S. Cardinal James Stafford told CBS News, "We build the image by accepting the reality that we're living in, and not being angry, and not being defensive."

How the scandals may affect the choice of a new pope will never be known, notes Pizzey. The penalty for anyone involved in the conclave who breaks the oath of secrecy, including technicians and even housekeepers, used to be decided by the new pope. But in one of his final acts, Benedict changed the penalty to excommunication.

Delia Gallagher, senior editor of Inside the Vatican magazine and a CBS News consultant, told "CBS This Morning" there is a "renewed sense of excitement at the Vatican" as the 115 voting cardinals prepare to select the next pope.

"We've had eight years of a rather difficult pontificate," Gallagher said, "The cardinals are almost looking forward to the opportunity to set a new direction, within the limits, of course, of what's available in the college of cardinals, who have all been nominated by Pope Benedict or by his predecessor Pope John Paul II.

"I do think there's that's sense of a new start, a fresh start for the church," Gallagher added.

Vatican officials say cardinals will begin meeting Monday to decide when to set the date for the conclave to elect the next pope.

But the rank-and-file faithful in the crowd Wednesday weren't so concerned with the future; they wanted to savor the final moments with the pope they have known for eight years.

"I came to thank him for the testimony that he has given the church," said Maria Cristina Chiarini, a 52-year-old homemaker who traveled by train early Wednesday from Lugo in central Italy with some 60 members of her parish. "There's nostalgia, human nostalgia, but also comfort, because as a Christian we have hope. The Lord won't leave us without a guide."

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